Method of preparing quinone



Nov. 1, 1938. N. H. VAGENiUS ET AL 2,135,363

METHOD OF PREPARING QUINCNE Filed Oct. 10, 195-1,

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IN VEN TORS M23 HAROL 0 V'Gf/V/l/ Ma By 120440 1[ ff/ao.

9 A TTORNEKS Patented Nov; 1, 1938 METHOD or PREPARING QUINONE Nels Harold Vagcnius, Chicago, Ill., and Rollo Kidd, Warrensville, Ohio Application October 10, Serial No. 147,726

7 Claims.

Our invention relates to a method of producing quinones, the phenol addition products thereof and hydroquinones, and more particularly to an improved method of producing such compounds by the oxidation of the phenols. In producing quinones or hydroquinones it has heretofore been proposed to oxidize aromatic hydrocarbons, such as benzene, by passing an electric current through an emulsion of benzene in an aqueous solution of a salt or mineral acid, the oxygen formed at the ucts are formed, such as resinous bodies, polyphenols, catechol, fatty acids, etc. In view of the side reactions which take place and the numerous other products which are formed it has heretofore been impractical to produce quinone, the phenol addition products thereof or hydroquinone, commercially by such processes.

We have made the discovery that if phenol is dissolved in an aqueous solution of a mineral acid or an acid salt in certain specified proportions and the temperature mainta ned within a specified range, phenols may be effectively and commercially oxidized to quinone or the phenol addition products thereof, depend ng upon the concentration of the phenol and the temperature at which the reaction takes place. The quinone, or the phenol addition products thereof, may then be reduced to hydroquinone.

While we do not desire to be limited in this respect, our process is particularly adapted for producing quinones or the phenol addition products thereof by the electrochemical oxidation of,

the phenols. Our invention also contemplates in its more specific form the production of quinone or the phenol addition products thereof by the oxidation of the phenols and their subsequent reduction preferably by electrochemical means,

to form hydroquinone.

It is therefore an object of our invention to proaddition products thereof, or hydroquinone, by means of which such compounds may be econom-.

ically and practically produced in an economical manner.

A further. object of our invention is to provide an improved process of producing quinone or the phenol addition products thereof by the electrochemical oxidation of phenol by'means of which.

high uniform yields of such compounds may be obtained.

Another object of'our invention is to a process of producing quinone-or the phenol addition products thereof from an electrolyte containing phenol by means of which the concentration of the phenol is maintained substantially constant and the quinone or a phenol addition product-thereof is quickly removed from the oxidation zone as soon ash is formed.

A further object of our invention is to provide an improved method of preparing hydroquinone by means of which quinone or a phenol addition product of quinone is first formed by the oxidation of a phenol and the hydroquinone is formed by the electrochemical reduction of the quinone or a phenol addition product thereof.

Another object of our invention is to provide an improved solution or electrolyte in wh ch quinone or a phenoladdition product thereof is insoluble at certain specified temperatures.

A still further object of our invention is to provide an improved process in which a phenol addition product of quinone is formed by the oxidation of a phenol, the product is subjected to electrochemical reduction to produce hydroquinone and phenol, and the phenol is again utilized in the process.

provide Although we do not desire to be limited in this respect we prefer to utilize the electrochemical method of oxidizing the phenols to produce qui-' nones or the phenol'addition products thereof, and this method has accordingly been illustrated in the accompanying drawing in which Fig. 1 is a diagrammatic view of an apparatus for producing quinone or the phenol addition products thereof; and Fig. 2 is a similar view of an apparatus for producing quinone or a phenol addition product thereof, and reducing it to hydroquinone. r

' In practicing our invention in accordance with I the method illustrated in the drawing, phenol or a homologue of phenol, such as cresol or xylenol, is dissolved in the electrolyte composed of a dilute solution of a mineral acid which does not react with the phenol, such as sulphuric acid or phosphoric acid. Solvents which are neutral or slightly acid may also be employed, such as the alkali bisulphates. For example, sodium bisulphate, aluminum sulphate and potassium aluminum sulphate have been found suitable. The electrolyte may be present in amounts ranging from 5% to 20%, although we do not desire to be limited in this respect as good results have -.been obtained when the electrolyte-is present in amounts as low as 1%. As the electrolyte we prefer to utilizean aqueous solution containing approximately 10% of sulphuric acid. As illustrated in the drawing, the electrolyte which contains the dissolved phenol is placed in a suitable ted; otherwise a precipitate containing undesirable products will be obtained. A direct current is then passed through the electrolyte.

The particular product which is formed will depend upon the temperature and the concentration of the phenol and whether a porous diaphragm is employed. If the concentration of the phenol is maintained low, for example, if not more than 1% is present and the temperature is kept below 12 C., the product will be composed principally of quinone, although some phenoquinone may be produced. If the concentration of the phenol is increased, a greater amount of phenoquinone will be produced. When the concentration of the phenol in the electrolyte is present in amounts ranging from 2% to 5% and the temperature is maintained below 12 C. phenoquinone will be produced. It will therefore be seen that the concentration of the phenol in the electrolyte is a material factor in determining whether quinone, phenoquinone or a mixture of these two compounds is formed.

While we have enumerated certain concentrations of phenol and specified certain temperatures at which quinone, phenoquinone or a mixture thereof will crystallize from the electrolyte, we prefer to maintain the electrolyte at a temperature below 7 C. The temperature of the electrolyte should be above the freezing point and below 12 C. The most desirable temperature, however, is slightly, above the freezing point, say from approximately3 to 5 0., because the quinone or phenoquinone is less soluble in the electrolyte at low temperatures. Suitable means, such as coils 6 through which.a cooling fluid or refrigerant is passed, may be provided to maintain the electrolyteat the desired temperature.

If itis desired to produce qfiinhydrone', the electrolyte is maintained at a temperature from approximately 12 to 17 0., preferably about C. In producing qi nhydrone it is also essential that the porous diaphragm be omitted.

.In p TQducing quinone, is essential that the concentration of the phenol should be maintained below 1% and in producing the addition products of quinone, such as phenoquinone or quinhydrone, it is essential that the concentration of the phenol in the electrolyte should be maintained below 5% and preferably below 3%,; otherwise undesirable side reactions will take place.

During the passage of the current the quinone or phenol addition product thereof is removed from the zone of oxidation, filtered as indicated at 8 from the mother liquor which may be returned to the electrolyte'by means of a suitable pump 9 and pipe Hi. the crystallized product being collected in the receptacle ll.

Although the voltage and current density at the anode may be varied within reasonable limits, we prefer to maintain the voltage below 3.5 volts. The current density at the anode should be ap-- proximately one ampere per twenty-eight square inches of surface. 5

To obtain uniform yields it is also desirable to maintain a substantially uniform concentration of-the phenol in the electrolyte. As the quinone or phenol addition product thereof is produced and removed from the oxidation zone, additional phenol should be added from the supply tank I. We have also found that the efliciency of the process may be improved by adding a small amount of a catalyst. For example, approximately one gram of chromium sulphate for each five hundred grams of electrolyte has been found suitable.

The quinone or phenol addition product thereof may, if desired, be reduced to hydroquinone by any of the usual processes. In accordance with our invention the quinone or phenol addition product thereof is first formed bythe method which has just been described and then reduced to hydroquinone by electrolytic reduction. The oxidation of the phenols to quinone or the phenol addition products thereof and the subsequent reduction may be performed separately or the two processes may be combined as illustrated in Fig. 2 of the drawing.

As illustrated in Fig. 2, the apparatus utilized in producing the quinone or phenol addition product thereof, is similar to that shown in Fig. 1 and the parts have consequently been designated by the same numerals. The quinone or phenol addition product thereof which is separated from the mother liquor by filtration or other suitable means is introduced into the electrolyte l2a of an electroplating cell or tank i2. The electrolyte in the reducing step may be composed of a dilute solution of sulphuric acid. It is not necessary that all of the quinone or the phenol addition product thereof should be in solution.

The cell I2 is provided with an anode 13 which may be formed of lead and a cathode M which may be formed of copper or bronze gauze similar to that utilized in the oxidation cell. The current is then passed through theelectrolyte utilizing approximately two volts and substantially the same current density as that employed during the'oxidation step. The temperature of the electrolyte is maintained at approximately 60 C. and if necessary suitable coils I5 through which a heating fiuid may be .passed are provided for this purpose.

The efficiency of the reduction step may also be improved by adding a suitable catalyst, such as titanium sulphate or tin sulphate. Approximately twp grams of the catalyst for each one hundred grams of electrolyte has been found satisfactory. The contents of the cell are then treated with av small amount of charcoal and allowed to cool.

If quinone or quinhydrone are first prepared they will be reduced to hydroquinone during the reduction step. If phenoquinone is-first prepared, during the reducing step the quinone is reduced to hydroquinone and the phenol floats upon the surface of the hydroquinone and may be removed by any suitable means or method, -such as by skimming or decantation, or as illustrated in the drawing the phenol may be returned to the supply tank I by means of a pump l6 and pipe 41. The hydroquinone which separates in the form of crystals may then be removed from the cell l2 and separated from the mother liquor at I8 by filtration or other suitable means and collected in the receptacle I9. The mother liquor may then be (I returned to the cell I 2 by pump 20 and pipe 2|.

As previously stated, we do not desire to limit our invention to the electrochemical method of producing quinone or the phenol addition products thereof. For example, the phenol in the concentration specified may be dissolved in a dilute solution of phosphoric or sulphuric acid, say a solution containing 1% to 20% of such acid or preferably from 5% to 20%, and the oxidation may be performed by means of suitable oxidizing agents such as ozone, hydrogen peroxide or persulphuric acid.

By oxidizing the phenol and maintaining the concentration of the phenol and the temperature within the range specified during the electrochemical method of oxidation, either quinone or a phenol addition product thereof, such as phenoquinone or quinhydrone, will precipitate and may be intermittently or continuously removed from the sphere of the reaction.

By utilizing the essential features of our invention it is also possible to prepare the phenol addition products of quinone. For example, if

phenol is added to or mixed with a chilled aqueous solution of quinone or an aqueous solution containing an electrolyte such as sulphuric or phosphoric acid, and the temperature is maintained below 12 C., or preferably below 7 C., phenoquinone will separate. In a like manner, by adding an aqueous solution of hydroquinone, or an aqueous solution of hydroquinone containing an electrolyte, to an aqueous solution of quinone, or mixing the solutions together and maintaining the temperature between 12 and 17 C., quinhydrone may be precipitated. It will therefore be seen that the quinhydrone may be readily converted into hydroquinone, or hydroquinone may in turn be converted into quinhydrone.

From the foregoing specification it will be apparent that we have provided a practical and effective method of producing quinone or the phenol addition products thereof by the oxidation of phenols which may be commercially and economically utilized in preparing the desired product.

It will also be seen that we have provided an economical and practical method of electrochemically oxidizing the phenols by means of which quinones, phenoquinones, quinhydrones and hydroquinones may be produced in an efiective and commercial manner.

It will also be apparent that we have provided an improved process by means of which phenols may be readily oxidized to quinone or the phenol addition products thereof without forming large quantities of other oxidation products and that the products thus obtained may be readily and effectively reduced to hydroquinone by electrochemical means.

It will also be understood that we have provided a method by means of which quinones or the phenol addition, products thereof may be effectively converted into hydroquinones by electro chemical reduction.

It will be understood in the specification and claims that the term quinone oxidation product of a phenol is intended to include not only quinone itself but also the phenol addition products thereof.

To those skilled in the art many modifications and widely differing embodiments of our invention will suggest themselves without departing from the spirit and scope thereof. Our disclosure, description and examples given herein are purely illustrative and are not intended to be in any sense limiting.

What we claim is:

1. The process of producing a quinone oxidation product of a phenol, at least part of which is obtained as a precipitated solid, which comprises passing a direct electric current through an aqueous solution of an acidic inorganic electrolyte which is a solvent for the phenol and which contains a substantial amount but less than three per cent of the phenol in solution while maintaining the electrolyte at a temperature ranging from 0 C. to 17 C.

2. The process of producing a quinone oxidation product of a phenol, at least part of which is obtained as a precipitated solid, which comprises passing a direct electric currentthrough an aqueous solution of an acidic inorganic electrolyte which is a solvent for the phenol and which contains a substantial amount but less than three per cent of the phenol in solution while maintaining the electrolyte at a temperature ranging from 0 C. to 17 C., and removing'the oxidation products from the zone of reaction as they are formed.

3. The process of producing a quinone oxidation product of a' phenol, at least part of which is obtained as a precipitated solid. which comprises passing a direct electric current through a dilute aqueous solution of sulphuric acid containing a substantial amount but less than three per cent of phenol to ,oxidize the phenol while maintaining the electrolyte at a temperature. ranging from 0 C. to 17 C.

4. The process of producing phenoquinone, at

least part of which is obtained as a precipitatedsolid, which comprises passing a direct electric current through an acidic inorganic electrolyte which is a solvent for phenol and which contains more than one per cent and less than three per cent of phenol in solution while main taining the electrolyte at a temperature ranging from 0 C. to 7 C. n

5. The process of producing quinone which comprises passing a direct electric current through an aqueous solution of an acidic inorganic electrolyte which is a solvent for phenol and which contains a substantial amount but less than one per cent of phenol while maintaining the temperature of the electrolyte between 0 C. and 7 C.

6. The process of producing a mixture of quinone and phenoquinone, at least part of which is obtained as a precipitated solid, which comprises passing a direct electric current through an aqueous solution of an acidic inorganic electrolyte which is a solvent for'phenol and which contains from one per cent to three per cent of phenol in solution while maintaining the temperature of the electrolyte between 0 C. and 7 C. 7. The process of producing quinhydrone, at

least part of which is obtained as a precipitated solid, which comprises passing a direct electric current between electrodes placed inan acidic inorganic electrolyte which is a solvent for phenol and which contains phenol in substantial amounts but less than three per cent while maintaining the temperature of the electrolyte between 12 C. and 17 C.

NE'LS HAROLD VAGENIUS.

RDLLO J. EDD. 

